There’s a good discussion here (kicked off by Jen) about providing different theme-color values in a web app manifest to match prefers-color-scheme in media queries.
Another good reason to use the currentColor value in SVGs.
On Ev’s blog, Marcin goes into great detail on theming an interface using CSS custom properties, SVG, HSL, and a smattering of CSS filters.
I was kind of amazed that all of this could happen via CSS and CSS alone: the colours, the transitions, the vectors, and even the images.
Harry demonstrates a really good use for CSS custom properties—allowing users to theme an interface.
Typographically thoughtful themes for NetNewsWIre. Even if you don't use the RSS reader, check out the gorgeous design of this site.